Drinking 500 ml of water caused a rapid increase in mean arterial pressure (peak increase of 12.6 mmHg) and heart rate, accompanied by an abrupt decrease in muscle sympathetic nerve activity.
Does drinking 500 ml of water alter blood pressure, heart rate, and muscle sympathetic nerve activity in healthy young men?
Water drinking causes a rapid, transient pressor response and tachycardia associated with a decrease in muscle sympathetic nerve activity, likely mediated by oropharyngeal stimulation rather than gastric distension.
Effect estimate: increase of 12.6 ± 2.1 mmHg at peak
Absolute Event Rate: 97.5% vs 88.4%
p-value: p=<0.001
To investigate the possible involvement of the sympathetic nervous system in pressor response during water drinking, muscle sympathetic nerve activity (MSNA), blood pressure (BP), and heart rate (HR) were continuously measured in healthy young volunteers throughout the experiments of a 5-min control, 2 min of drinking 500 ml water, and a 28-min recovery. To avoid the effects of water passing through the oropharyngeal and esophageal regions and/or effects of swallowing, an equal amount of water was directly infused to the stomach through a stomach tube for 2 min. Water drinking caused a transient increase in mean arterial pressure (MAP) and HR immediately after drinking (DeltaMAP, 12.6 +/- 2.1 mmHg; DeltaHR, +19.9 +/- 1.7 beats/min at the peak). An abrupt decrease of MSNA was observed directly during water drinking (Deltaburst rate, -6.9 +/- 1.3 bursts/min; Deltatotal activity, -2,606 +/- 491 U/min), and it increased to the baseline level thereafter. Gastric infusion had little or no effect on MAP, HR, and MSNA. The present study demonstrated that a pressor response during water drinking was associated with the attenuation of MSNA and not generated by gastric infusion of water at the same rate as in this drinking manner. In conclusion, the rapid rise in BP might be caused through stimulations from the oropharyngeal region, swallowing-induced factors, and/or a feedforward mechanism by a central descending signal from the higher brain centers.
Endo et al. (2002) studied Healthy (n=19). Water drinking vs. Gastric infusion or time control was evaluated on Mean arterial pressure (MAP) (increase of 12.6 ± 2.1 mmHg at peak, p=<0.001). Drinking 500 ml of water caused a rapid increase in mean arterial pressure (peak increase of 12.6 mmHg) and heart rate, accompanied by an abrupt decrease in muscle sympathetic nerve activity.